1. Field of the Invention
This invention relates to the removal of hydrogen sulfide from gases, and more particularly to a process for removing hydrogen sulfide from hydrogenated Claus process tail gas in which the hydrogen sulfide is converted to elemental sulfur.
2. Description of the Prior Art
With the increasing concern over the pollution of the atmosphere, great demands have been made on industry to produce pollution-free products and to do so in a pollution-free manner. One area of particular concern has been the release of sulfur and its compounds into the atmosphere during the refining of petroleum, the sweetening of natural gas, the processing of ore, the destructive distillation of coal, and other processes which produce sulfur-containing gases.
The Claus process is widely employed for the desulfurization of hydrogen sulfide-containing gases and is about 90 to 97 percent effective in converting hydrogen sulfide to elemental sulfur. While substantial amounts of sulfur are recovered and, thus, prevented from being released into the atmosphere, in many instances it is necessary to further treat the Claus process tail gas to make it acceptable for discharge into the atmosphere. One process particularly useful for treating these tail gases is the Beavon sulfur removal process described in U.S. Pat. No. 3,752,877, which process involves the hydrogenation of the Claus process tail gas to convert the various sulfur compounds to hydrogen sulfide, and them employing a process, known as the Stretford process, to remove the remaining hydrogen sulfide. The Stretford process is a well-known process for converting hydrogen sulfide to elemental sulfur and is described in U.S. Pat. Nos. 2,997,439, 3,035,889, and 3,097,926.
However, while the Stretford process has been relatively successful, it has been discovered that when used to treat hydrogenated Claus process tail gas, one of the principal constituents of the washing solution, anthraquinone disulfonate, is chemically consumed, which necessitates frequent addition of this expensive chemical to maintain the proper concentration of this constituent in the washing solution. This invention is directed to reducing the consumption of anthraquinone disulfonate (ADA) and to the improvement of the Stretford process when used to treat hydrogenated Claus process tail gas.
Accordingly, a principal object of this invention is to provide an improvement in the Stretford process for the removal of hydrogen sulfide from gases and its conversion to elemental sulfur.
Another object of this invention is to provide an improvement in the Stretford process when used to treat hydrogenated Claus process tail gas.
Yet another object of this invention is to reduce the excessive amounts of ADA consumed during the Stretford process when used to treat hydrogenated Claus process tail gas.
Further objects and advantages of this invention will be apparent to those skilled in the art from the following description.